Apple & pear cordons

I'm hopine to create a screen to my vegie patch using cordo apples & pears grown on a timber frame with wires. The screen will be about 9m long with a gap in the middle for the footpath; can anyone offer any advice on the following:

1) Any recommended suppliers.

2) Recommended desert cultivars / can I have a range of different cultivars or am I best sticking to 1 type of apple / pear.

3) Recommended spacing, want it as dense as possible while still being productive.